Macas-Rubalcava et al., in J. Photochem. Photobiol. (2017) B 166:3543, investigated the mechanism of action of several

Macías-Rubalcava et al., in J. Photochem. Photobiol. (2017) B 166:35–43, investigated the mechanism of action of several compounds that might serve as new herbicides. One of these new compounds (#7) inhibited photophos-phorylation. The data below show the effects of compound 7 on uncoupled electron transport in isolated illuminated chloroplasts. The scheme below is a linear version of the Z-scheme in Figure 15.11(b), showing the sequence of electron transport through PSII and PSI. Arrows show the sites of electron donation and acceptance for various artificial donors/acceptors. Vertical dashed lines show sites of inhibition by Tris and DCMU. 

Based on these data, predict the site of action of the new compound. Explain your reasoning.

Transcribed Image Text:

H₂O OEC Tris P % Activity 680 DPC 100 80 60 40 20 0 0 - Ph - HALO 50 ✔ 100 150 200 250 Compound 7 [uM) SiMo QA DCMU DCBQ QB DCPIP 300 DCPIP DPC MV H₂O H₂O PQH₂ MV DCPIP bof P100 pod SiMo DCBQ PC